1. Field of the Invention
The present invention relates to radio frequency switches. More specifically, the present invention relates to a latchable, magnetically actuated, ground plane-isolated radio frequency microswitch.
2. Background Art
Switches are typically electrically controlled two-state devices that open and close contacts to effect operation of devices in an electrical or optical circuit. Relays, for example, typically function as switches that activate or de-activate portions of electrical, optical or other devices. Relays are commonly used in many applications including telecommunications, radio frequency (RF) communications, portable electronics, consumer and industrial electronics, aerospace, and other systems. More recently, optical switches (also referred to as “optical relays” or simply “relays” herein) have been used to switch optical signals (such as those in optical communication systems) from one path to another.
Although the earliest relays were mechanical or solid-state devices, recent developments in micro-electro-mechanical systems (MEMS) technologies and microelectronics manufacturing have made micro-electrostatic and micro-magnetic relays possible. Such micro-magnetic relays typically include an electromagnet that, when energized, causes a cantilever to make or break an electrical contact. When the magnet is de-energized, a spring or other mechanical force typically restores the cantilever to a quiescent position. Such relays typically exhibit a number of marked disadvantages, however, in that they generally exhibit only a single stable output (i.e., the quiescent state) and they are not latching (i.e., they do not retain a constant output as power is removed from the relay). Moreover, the spring required by conventional micro-magnetic relays may degrade or break over time.
Non-latching relays are known. The relay includes a permanent magnet and an electromagnet for generating a magnetic field that intermittently opposes the field generated by the permanent magnet. This relay must consume power in the electromagnet to maintain at least one of the output states. Moreover, the power required to generate the opposing field would be significant, thus making the relay less desirable for use in space, portable electronics, and other applications that demand low power consumption.
Furthermore, microwave switches have been realized in mechanical or semiconductor technologies. While mechanical switches are characterized by low signal loss and good isolation, they have slow switching speeds, consume considerable power, and are bulky. Conversely, while semiconductor switches (e.g., Field Effect Transistors, Positive-Intrinsic-Negative diodes, etc.) enjoy high switching speeds, low power consumption, and compactness, in their ON states they contribute to signal loss, and in their OFF positions they suffer from inferior isolation. They also have limited switching current capacities. Although developed for microwave frequencies, these switches can be used throughout the radio frequency (RF) spectrum.
However, the development of MEMS has yielded an opportunity to realize RF switches that capitalize on the desirable features of both mechanical and semiconductor switches, while limiting the unwanted characteristics of these earlier technologies. Particularly, a bi-stable, latching switch that does not require power to hold the states is desired. Such a switch should also be reliable, simple in design, low-cost and easy to manufacture, and should be useful in RF, optical, and/or electrical environments.